Ninh Binh is often called Ha Long Bay on land, and geologically that is fair enough — the same limestone, with rivers instead of sea between the towers. The experience is nothing like it, though. The boats are small and unpowered, the person rowing sits directly behind you, and for three hours on the river you hear almost no engines at all.
We use the Trang An route rather than Tam Coc, even though Tam Coc is nearer and cheaper. Trang An takes you through nine flooded caves instead of three, the landing is large enough that you rarely queue, and you are not followed by vendor boats the way you are on the other route. The trade-off is about an extra hour on the water.
Mua Cave comes last because it is the hardest part of the day: nearly 500 uneven stone steps, without a continuous handrail, and the light is kinder in the late afternoon. Anyone who prefers to skip the climb can stay at the lotus pond below, which is worth sitting by in its own right. The trip runs out and back in a day, so there is no need to check out of your Hanoi hotel.